Some bacterial toxins can survive boiling or frying, so reheating spoiled food does not necessarily make it safe. The warning is consistent with US CDC guidance on staphylococcal food poisoning.
Andrey Tatarchik, a senior lecturer in hygiene at Pirogov University’s Institute of Preventive Medicine, told TASS that staphylococcal toxin can withstand heat. The US Centers for Disease Control and Prevention likewise says cooking can kill Staphylococcus bacteria but does not destroy toxin already present in food.
He cited cottage-cheese pancakes made with expired tvorog as an example: frying does not guarantee that harmful substances, if already formed, will be eliminated. Tatarchik said food should not be judged safe just because it has no unpleasant smell or visible change in colour or taste.
Risk also depends on the label and storage conditions. The UK Food Standards Agency says foods carrying a use-by date should not be eaten after that date, even if they look and smell normal. A best-before date, by contrast, relates mainly to quality.